336/B9042
  • Brand
    JCB
  • Article
    336/B9042
  • Machine system
    Hydraulic system
  • Part type
    Valve spool
  • Machine brand
    JCB
  • Manufacturing type
    Original
  • All the features
In stock
0.00 ₺
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Priority valve spool 336/B9042 is a genuine JCB part for the JCB machines.

The spool is a precision-machined steel rod in a valve section that decides which side of the cylinder gets the oil; as the control lever moves, the spool slides and opens or closes the passages. The lands and notches on it set the speed and smoothness of the movement, so the spools of different sections in one block differ and are identified by letter. A scored or worn spool causes internal leakage, creep and sticking. Leaking spool seals show as oil around the control levers. The spool is supplied new, and its surface must be protected in transit, since even a small scratch can cause leakage. The spool is made of steel.

Specifications


Part number336/B9042
ManufacturerJCB
Production typeOriginal
Part typeValve spool
System / groupHydraulic system
Machine makeJCB

Compatibility

The spool belongs to the steering circuit priority valve, which sends pump flow to the steering first. The catalogue also has the aftermarket version of this part. Other parts are in Hydraulic valves.

Fitting

Oil the spool with clean hydraulic oil and slide it into the bore without force, turning it slightly; if it binds, recheck the bore and spool. After assembly, work the lever in every direction to confirm the spool moves freely.

Specifications

  • Machine system
    Hydraulic system
  • Part type
    Valve spool
  • Machine brand
    JCB
  • Manufacturing type
    Original
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JCB 3CX / 4CX 07/10/2026 49
JCB 3CX and 4CX hydraulic circuit diagrams by build year, with component keys
There is no single hydraulic circuit for the JCB 3CX and 4CX backhoe loader: it depends on the build year and the pump type. Section E of the JCB service manual (publication 9803/3290-14) gives separate circuits for the gear pump 3CX built before and after September 2007, for the variable flow 4CX (7-spool and 6-spool), and for the 3C-14 (214e) and 3C machines. Below you will find the circuits themselves, the component keys and some notes on tracing the oil flow through a circuit.
Useful articles 07/10/2026 40
JCB 3CX / 4CX Hydraulic Pressure: Settings, Pressure Testing and Causes of Low Pressure
On JCB 3CX and 4CX backhoe loaders with a gear pump, the working pressure of the hydraulic system is limited by the main relief valve in the loader valve: 236–241 bar on machines up to serial number 964124 and 248–252 bar on machines from serial number 964125 (standard and high-pressure hydraulics). It is checked with a 0–400 bar pressure gauge connected to the loader valve test point, with the engine at 1500 rev/min and the oil warmed to 50 °C. Below are the settings, the test procedure and the reasons why pressure drops, taken from the JCB service manual (Section E).
JCB 3CX / 4CX 07/10/2026 18
JCB 3CX / 4CX Hydraulics: Circuit Diagrams, Pumps and Relief Valve Pressures
Section E of the JCB service manual (publication 9803/3290-14) deals with the hydraulic system of the JCB 3C, 3CX and 4CX backhoe loaders. It brings together technical data for the pumps and valve blocks, hydraulic circuits for machines of different build years, valve operation, fault finding tables, and the procedures for pressure testing and for overhauling the pump, valves and rams. The section PDF runs to 302 pages.
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